JPS6360073B2 - - Google Patents

Description

[Detailed description of the invention]

(Object of the invention) The present invention relates to a novel coating composition that has excellent corrosion resistance for zinc and zinc alloys, and its object is to provide a coating composition that does not use any conventional antirust pigments or corrosion inhibitors. The purpose of the present invention is to create an air-drying coating that has excellent physical properties such as corrosion resistance and adhesion to zinc and zinc alloys, water resistance, salt water resistance, and moisture resistance. (Industrial Application Fields) Zinc and zinc alloys have been widely used in industry in recent years, in addition to being used alone, as galvanized steel and zinc alloy plated steel. The current situation is that it is being processed. Among these, coating agents are most commonly used because they are easy to operate, efficient, and relatively inexpensive. There are two types of coating materials: colored types that contain pigments and transparent types that do not, and which one to use is mainly determined by the intended use and the environment in which it is placed. (Prior art) Conventional zinc and zinc alloy anticorrosion coatings include (1) synthetic resins such as epoxy resins, polyurethane resins, acrylic resins, vinyl resins, and chlorinated rubber, zinc chromate, calcium lead oxide, zinc phosphate, etc. (2) Polyvinyl butyral resin alone or a mixed resin with alkyd resin, epoxy resin, phenolic resin, etc. added to it, zinc chromate, and colored pigments. A wash primer consisting of a main ingredient made by adding extender pigments, etc., and an acid solution whose main ingredient is phosphoric acid. (3) A transparent etching primer made by adding chromic anhydride, phosphoric acid, etc. as a corrosion inhibitor to polyvinyl butyral resin or epoxy resin. (4) petrolatum, petrolatum oxide,
Made by adding metal salts of lanolin and petrolatum oxide, metal salts of alkylbenzenesulfonic acid and alkylnaphthalenesulfonic acid as rust preventive agents to mineral oil, lanolin, etc. and dissolving or dispersing them in an organic solvent. (5) Synthetic resin clears made by dissolving single or mixed resins such as acrylic resins, polyurethane resins, epoxy resins, petroleum resins, coumaron resins, cyclized rubbers, and vinyl copolymer resins in organic solvents can be mentioned. The coating agent (1) has relatively excellent corrosion resistance and is used industrially as an anticorrosion coating agent for colored finishing. Among the anticorrosive pigments contained in these, zinc chromate contains hexavalent chromium. Calcium leadate is a poisonous substance, and calcium leadate is a compound of lead, a toxic heavy metal, which poses problems in terms of occupational health and safety, and zinc phosphate has a slightly inferior corrosion resistance. Washing primer (2) and etching primer (3) both contain harmful chromium compounds, and (4) is a translucent coating based on petroleum wax or lanolin, which does not give a good appearance to the paint film. It is a non-drying sticky soft film and has problems such as not being able to be overcoated. (5) is a synthetic resin-based transparent coating agent with drying properties,
Although it has good transparency and gloss, there are currently few effective corrosion inhibitors for zinc and zinc alloys, so the coating itself has poor corrosion resistance, and it corrodes in humid, salty, etc. environments. There is a problem that whitening and blistering of the paint film are likely to occur. (Structure and Effects of the Invention) The present inventors have discovered that a thin film that is naturally dried has excellent physical properties such as corrosion resistance and adhesion to zinc and zinc alloys, water resistance, salt water resistance, moisture resistance, etc., and also has the problems of the prior art products described above. As a result of intensive research to develop anti-corrosion coatings for zinc and zinc alloys that are free of corrosion, we have found that the coating binder is soluble in organic solvents and has a softening point of 70 to 180.
℃, 20 to 80 parts (parts by weight, the same applies hereinafter) of polyamide resin with an acid value of 15 or less and a total amine value of 15 or less, and 80 to 20 in terms of silica (SiO ₂ ) of organosilica sol
By using a mixture of parts, corrosion resistance and adhesion to zinc and zinc alloys, water resistance, and
The present inventors have discovered that the product has excellent physical properties such as salt water resistance and moisture resistance, and can solve all of the problems of the prior art products mentioned above, leading to the completion of the present invention. That is, the present invention is a coating composition for zinc and zinc alloy corrosion protection containing a binder, an organic solvent, and optionally a coloring pigment, an extender pigment, an additive, etc., wherein the binder is soluble in the organic solvent and has a softening point of 70 to 70. 180℃,
Corrosion-preventing zinc and zinc alloy, characterized by being a mixture of 20 to 80 parts of a polyamide resin with an acid value of 15 or less and a total amine value of 15 or less, and 80 to 20 parts of organosilica sol in terms of silica (SiO ₂ ). Concerning coating compositions. The polyamide resin used as the binder component of the present invention is a resin having an amide group (-CO-NH-) in the molecule, which is produced by condensation of a polybasic acid and a polyvalent amine, condensation of an aminocarboxylic acid, etc.
and its modified resin, which is soluble in organic solvents, has a softening point of 70 to 180°C, preferably 90 to 160°C, and an acid value of
Those having a total amine value of 15 or less, preferably 10 or less, and 15 or less, preferably 10 or less, can be used. If the softening point of the polyamide resin is less than 70℃, water resistance,
Moisture resistance is poor, and if the temperature exceeds 180°C, solubility deteriorates, which is not preferable. If the acid value exceeds 15, the anticorrosion properties will be poor, and if the total amine value exceeds 15, the compatibility with organosilica sol, which is another binder component of the present invention described later, will deteriorate, so both are unfavorable. Another compound used as a binder component of the present invention
Organosilica sol consists of 15 ultrafine particles of silica (particle size 5 to 100 mμ) in an organic medium.
Colloidal silica is stably dispersed at a concentration of ~60% (the same applies below weight%), and organosilica sol is produced by adding acid to an alkali silicate such as sodium silicate or potassium silicate to refine the silicate sol.
There are two methods: by dispersing it in an organic medium, and by hydrolyzing and condensing alkoxysilanes such as tetramethoxysilane, tetraethoxysilane, and methyltriethoxysilane, and/or their initial condensates in an organic medium. In the latter case, a portion of unreacted alkoxy groups remains, but products prepared by either method can be used. The organic media used in the production of organosilica sol include methyl alcohol, ethyl alcohol,
Examples include n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, acetone, methyl ethyl ketone, methyl cellosolve, cellosolve, butyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and the like.
Any of the organosilica sols made using these organic media can be used as the binder component of the present invention, but from a price point of view, methyl alcohol silica sol, ethyl alcohol silica sol, and ethyl alcohol silica sol using methyl alcohol, ethyl alcohol, and isopropyl alcohol as the medium are Isopropyl alcohol silica sol is preferred. Of course, there may be one type of organosilica sol, or two or more types of organosilica sol may be used. As the binder component of the present invention, based on 20 to 80 parts, preferably 30 to 70 parts of the above polyamide resin,
Organosilica sol in terms of silica (SiO ₂ )
A mixture of 80 to 20 parts, preferably 70 to 30 parts is used. If the mixing ratio of organosilica sol to polyamide resin is less than 80:20 (weight ratio, hereinafter omitted), the corrosion resistance will be poor.
If the ratio exceeds 20:80, the coating film becomes brittle and has poor flexibility, adhesion, and corrosion resistance, which is not preferable. The organic solvent used in the present invention is not particularly limited, and any known organic solvent can be used as long as it dissolves the polyamide resin and organosilica sol mixture, such as methyl alcohol, isopropyl alcohol, n - Alcohol solvents such as butyl alcohol, aromatic hydrocarbon solvents such as toluene, xylene, decalin, and tetralin, ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone, and ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; Examples include ether alcohol solvents such as ethyl cellosolve, butyl cellosolve, and propylene glycol monoethyl ether, and ether ester solvents such as ethyl cellosolve acetate and butyl cellosolve acetate, and these may be used alone or in combination of two or more. . The amount of organic solvent used is
They vary depending on the purpose and are not fixed. Coloring pigments and extender pigments are not particularly limited, and include those used in general coating materials.
It can be used appropriately as needed. Specific examples of such pigments include coloring pigments such as titanium dioxide, red iron oxide, carbon black, and phthalocyanine blue, and extender pigments such as talc, kaolin, mica, and barium sulfate. Examples of additives include antifoaming agents, leveling agents, dispersants, anti-settling agents, thickeners, etc., and any of these can be used if necessary. In addition to the above-mentioned components, the composition of the present invention may optionally contain metal powders such as aluminum powder, zinc powder, and stainless steel powder, flaky iron oxide, glass powder, glass flakes, porcelain powder, and mica flakes. etc. can be used. The composition of the present invention includes an organic solvent and, if necessary, a coloring pigment, an extender pigment,
It is manufactured by adding additives and the like and dissolving, mixing and dispersing them using, for example, a dissolver, roll mill, sand mill, etc. The zinc and zinc alloy anticorrosive coating composition of the present invention thus obtained can be coated using conventional coating methods such as brushing, air spraying, airless spraying,
It can be applied suitably by roller coating, dip coating, electrostatic coating, etc., and when air dried, it has a thin film that has corrosion resistance against zinc and zinc alloys, and various physical properties such as adhesion, water resistance, salt water resistance, and moisture resistance. Because of its excellent properties, it is suitable for all kinds of objects using zinc and zinc alloy materials, as well as galvanized steel materials and zinc alloy plating steel materials, such as building materials, fences, gates, supports, poles, guardrails, signboards, steel towers, pipes, wires, and marine structures. It has excellent effects as an anti-corrosion coating for objects, vehicles, ships, construction machinery, bridges, etc. According to the present invention, such remarkable effects can be obtained because a mixture of the specific polyamide resin and organosilica sol in a specific ratio is used as the binder of the coating material. Although the mechanism is still not clear, it is presumed as follows. That is, on the surface of the silica particles of the organosilica sol in the composition, there are many -OH groups, which are reactive polar groups bonded to silicon, and when applied to zinc and zinc alloy objects, the polar groups (-
(OH groups) are regularly oriented toward the object to be coated and react with the zinc on the surface of the object to form a three-dimensional network structure, creating a strong barrier layer with excellent adhesion and anti-corrosion properties. The remaining -OH groups are dehydrated and condensed to form interparticle siloxane bonds (-Si-O-Si-),
It has the property of forming a coating film with excellent water resistance, salt water resistance, moisture resistance, and heat resistance. Polyamide resin, another binder component, has good compatibility with organosilica sol, and has an amide group (-
Polar groups such as CO-NH-), amino groups (-NH ₂ ), and carboxyl groups (-COOH) are integrated with silanol groups (-Si-OH) on the surface of silica particles through hydrogen bonds, and their film-forming properties are poor when used alone. The polyamide resin is hygroscopic (0.1-0.3%;
ASTM D570, 24 hours), it has the effect of promoting the hydrolysis of the alkoxy groups partially present in the organosilica sol and activating the silica, and the effects of these two components are excellent together. It is believed that various physical properties such as corrosion resistance, water resistance, salt water resistance, and moisture resistance can be obtained. The above-mentioned excellent physical properties of a thin film can be obtained due to the formation of an integrated tough barrier layer through the reaction with the metal of the object to be coated, and the activation of silica due to the hygroscopicity of the polyamide resin. I think that the. In addition, excellent results were obtained for the air-dried coating film of the composition of the present invention, baking (140°C, 30 minutes), and physical property test results of the coating film, with no difference between the two.
The action of the binder component mentioned above can be achieved even without heating.
It seems to occur at room temperature. Resins that are compatible with the organosilica sol of the present invention include polyvinyl butyral resins, epoxy resins, acrylic resins, phenolic resins, ethyl cellulose resins, etc. in addition to the above-mentioned specific polyamide resins. The results showed that all of the resins other than the above-mentioned polyamide resins had poor corrosion resistance, water resistance, and moisture resistance, and were far inferior to the compositions of the present invention, which yielded excellent results. This is thought to be because the polyamide resin has the above-mentioned characteristics not found in other resins. Synthesis Examples, Examples, and Comparative Examples are shown below, but the present invention is not limited to the examples described below. Note that parts are parts by weight, and % is weight %. Synthesis example (synthesis of organosilica sol by hydrolysis of alkoxysilane) Tetraethoxysilane initial condensate (“Ethylsilicate 40” manufactured by Tama Chemical Industry Co., Ltd.) 100 parts Isopropyl alcohol 25〃 Ethyl alcohol 25〃 10% phosphoric acid aqueous solution 16〃 166 Place the remaining components except for the 10% phosphoric acid aqueous solution into a reaction vessel, add the 10% phosphoric acid aqueous solution dropwise over 1 hour while stirring, then gradually raise the temperature to 80℃, and then add the remaining ingredients at the same temperature. The reaction was carried out for 10 hours to obtain an organosilica sol. The silica (SiO ₂ ) content of this material is
It was 24%. Examples 1 to 11 Add an organic solvent to the polyamide resin at the blending ratio shown in Table 1, stir with a dissolver to completely dissolve it, then add organosilica sol and further stir with a dissolver to mix uniformly. A coating composition for corrosion protection of zinc and zinc alloys according to the invention was obtained. Examples 12, 13 Add an organic solvent to polyamide resin at the blending ratio shown in Table 1, stir with a dissolver to completely dissolve, add pigments and additives to the solution, and run a three-roll mill four times. After uniformly dispersing the mixture, organosilica sol was added and mixed uniformly by stirring with a dissolver to obtain a coating composition for zinc and zinc alloy anticorrosion of the present invention.

【table】

【table】

[Table] Comparative Examples 1 to 5, 10 Comparative zinc and zinc alloy anticorrosive coating compositions were obtained in the same manner as Examples 1 to 11 at the blending ratios shown in Table 2. However, in the case of Comparative Example 4, the polyamide resin component DPX850 is not compatible with the methanol silica sol of the organosilica sol component, and in the case of Comparative Example 5, the polyamide resin component Macromelt 6300 does not dissolve in the organic solvent. It was not possible to create the coating compositions of Nos. and 5. Comparative Examples 6 to 9 After adding an organic solvent to the resin and stirring with a dissolver to completely dissolve it in the proportions shown in Table 2,
Organosilica sol was added and further stirred with a dissolver to mix uniformly to obtain comparative zinc and zinc alloy anticorrosive coating compositions. Comparative Examples 11 and 12 Comparative zinc and zinc alloy anticorrosion coating compositions were obtained in the same manner as in Examples 12 and 13 at the blending ratios shown in Table 2.

【table】

[Table] Each zinc and zinc alloy anticorrosive coating composition obtained in the Examples and Comparative Examples was tested and evaluated by the following method. Preparation of test piece Test plate {Test plate a: Electrogalvanized steel plate (70×
150 x 0.8 mm), test plate b: electrolytic zinc alloy plated steel plate (70 x 150 x 0.8 mm)}, and after drying at room temperature for 4 days, test (1) Film thickness (Co., Ltd.) ) The dry film thickness of the test piece was measured using a film thickness meter LX-100 manufactured by Kett Science Institute. (2) Salt spray resistance After making diagonal cross cuts on the coating film on the surface of the test piece with a cutter knife, JISZ
Tested for 100 hours according to the salt spray test method of 2371, and observed the condition of the applied surface. No abnormality (〇),
The evaluation was divided into three levels: slightly rusted (△) and considerably rusted (×). (3) Water resistance After immersing the test piece in tap water at 20℃ for 30 days, the condition of the coated surface was observed and divided into three grades: no abnormality (〇), slight whitening (△), and considerable whitening (×). It was evaluated. (4) Salt water resistance The test piece was placed in a 3% sodium chloride aqueous solution at 20℃ for 30 minutes.
After soaking for a day, the condition of the coated surface was observed and rated as 3: no abnormality (〇), slight rust (△), and considerable rust (×).
The evaluation was divided into stages. (5) Moisture resistance After testing the test piece in a humidity tester at 50℃ and 98%RH for 30 days, the condition of the painted surface was observed: no abnormality (○), slight rust or whitening (△), considerable The evaluation was divided into three grades: rusting or severe whitening (×). (6) Adhesion Conduct a substrate test (JIS K 5400-6.15) and observe the adhesion state of the paint film after peeling off the Sellotape.
It was evaluated by the score. 10 points: Each cut is thin and smooth on both sides, and there is no peeling at the intersection of the cuts and at the first glance of the square. 0 points: The area of peeling is
More than 65% of the total square area. (7) Flexibility It takes 1 second to bend around a steel mandrel with a diameter of 6 mm.
Bend it 180 degrees, observe the condition of the coating on the bent surface,
The evaluation was divided into three grades: no abnormality (◯), slight cracking (△), and full-scale cracking (x). These results are shown in Table 3.

【table】

[Table] As is clear from Table 3, the zinc and zinc alloy corrosion-resistant coating compositions of the present invention shown in Examples 1 to 13 gave good results in all items for both galvanized steel sheets and zinc alloy-plated steel sheets. was obtained, and it was demonstrated that it was a thin film that dried naturally and had excellent corrosion resistance, water resistance, salt water resistance, moisture resistance, and adhesion. On the other hand, Comparative Examples 2 and 12, in which the mixing ratio of organosilica sol (SiO ₂ equivalent) to the polyamide resin of the binder component was less than the specified ratio, had poor salt water spray resistance and salt water resistance, and Comparative Example 1, in which the mixing ratio exceeded the specified ratio. , 10, and 11 had poor salt spray resistance, salt water resistance, adhesion, and bending resistance. Comparative Example 3, which used a polyamide resin with an acid value higher than the specified value, had poor salt water spray resistance and salt water resistance, and Comparative Example 4, which used a polyamide resin with a total amine value higher than the specified value, had a combination of polyamide resin and organosilica sol. In Comparative Example 5, which used a polyamide resin with poor compatibility and a softening point higher than the specified value, the coating compositions of Comparative Examples 4 and 5 could not be created because the polyamide resin did not dissolve in the organic solvent. Comparative Examples 6 to 9, in which other resins were used instead of the polyamide resin as the binder component, had better salt spray resistance, water resistance, salt water resistance, and moisture resistance than the compositions of the present invention, although there were slight differences depending on the type of resin. The results showed that the quality was significantly inferior.

Claims (1)

[Scope of Claims] 1. Consists of a binder, an organic solvent, and if necessary, a coloring pigment, an extender pigment, an additive, etc., and the binder is soluble in the organic solvent and has a softening point of 70°C to 180°C,
A zinc and zinc alloy preventive material characterized by being a mixture of 20 to 80 parts by weight of a polyamide resin with an oxidation rate of 15 or less and a total amine value of 15 or less, and 80 to 20 parts by weight of organosilica sol in terms of silica (SiO ₂ ). Edible coating composition. 2. The corrosion-protective coating composition for zinc and zinc alloys according to claim 1, wherein the organosilica sol is one or a mixture of two or more of methyl alcohol silica sol, ethyl alcohol silica sol, and isopropyl alcohol silica sol.